Controller.



PATENTED NOV. 22, 1904-.

E. SGHATTNER.

CONTROLLER.

APPLICATION FILED MAY 13, 1904. I v NO MODEL. .2 SHEETS-SHEET 1-- Fig.1.

UNITE STATES Patented November 22, 1904.

PATENT OFFICE.

ERAL ELECTRIC COMPANY,

A CORPORATION OF NEW YORK.

CONTROLLER.

SPECIFICATION forming part of Letters Patent N o, 77 5,501 dated November 22, 1904.

I Application filed May 13, 1904. Serial No. 207,759. (No model.)

To all whom it Meaty concern.-

Be it known that I, ERNEST SOHATTNER, a subject of the King of Great Britain, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Controllers, of which the following is a specification.

This invention relates to controllers for electric motors, and particularly to that type of controllers known as motor-starting rheostats. Its object is to provide such arheostat by which a smooth resistance gradient will be obtained, and I accomplish this by employinga self-reducing resistance-that is, a resistance the ohmic value of which is decreased by the passageof the currentthrough it.

Prior to my invention the common practice has been to provide motor-starting rheostats with wire resistances connected to studs arranged in an arc of a circle and a pivoted switch-arm cooperating with the studs. With such a device the resistance is cut into and out of the motor-circuit in steps. Obviously a starting-rheostat with which asmooth resistance gradient is obtained would give more satisfactory results. -It has long been known that certain substances possess a negative temperature coefi icient of resistance-that is, they decrease in ohmic value when heated-and such substances have been termed self-reducing resistances. Some substances possess this characteristic to such an extent that they may be used in place of hand-operated resistances in electric circuits where it is desirable that the resistance be great when the current is first applied and shall then be gradually reduced. Among such substances magnetite possesses this self-reducing characteristic to a marked degree, and is thus'particularly well suited for use as a startingresistance for electric motors and for similar purposes.

In a companion application filed by me March 31, 1904, and serially numbered 200, 881, is described a self-reducing-resistance unit having magnetite and a silicate mixed in proper proportions and held within a tube under pressure. My present invention relates to a motor-starting rheostat employing such a self-reducing resistance and provided with switching mechanism by which the circuit to the motor may be closed through the resistance, and in order that the self-reducing-resistance material may cool, and thus be in readiness to again properly start the motor whenever that is desired, I arrange the parts so that the resistance may be short-circuited as soonas the motor is up to speed.

My invention further comprises means whereby the resistance is short-circuited automatically when its ohmic value has fallen to a predetermined amount.

The novel features of my invention will be definitely indicated in the claims appended hereto.

The details of construction and the mode of operation of my improved motor-starting rheostat will be better understood by reference to the following description, taken in connection with the accompanying drawings, which show the preferred embodiment of my invention.

In the drawings, Figure l is a plan view of the rheostat. Fig. 2 is a diagrammatic view of the same. Fig. 3 is an elevation of the resistance; and Figs. 4 and 5 are a plan and diagrammatic view, respectively, of a modification.

Referring first to Figs. 1 and 2, 1 indicates a base-plate of soapstone or other suitable insulatingmaterial, and 2 is a switch-arm provided with an operating-handle 3 and pivotally mounted on a bolt 4, supported on the base-plate. Secured to the under side of switch-arm 2 is a leaf-spring 5, arranged to engage a contact-segment 6 when the switcharm is turned on its pivot. Secured to the switch-arm is an armature 7, which when the arm is moved to the limit of its travel engages the pole-pieces of a magnet 8, mounted on the base-plate, and the arm is then held in this position by the magnet as long as the latter is energized. A coiled spring 9, having one end attached to the switch-arm 2 and the other to a stud mounted on the base-plate, is arranged to return the arm to the off position when magnet 8 is deenergized. Independently pivoted on the bolt 4 is an auxiliary switch-arm 10, preferably of copper, having secured to w as its end a curved cross-piece 11., of iron or other material of good permeability. Mount- 1 ed on the base-plate is a switch-clip 12, which is engaged by the auxiliary switch-arm 1O when the latter is moved to its final position. The rheostat is mounted on its support in a I weakened that it no longer retards the switchvertical position, so that the auxiliary switch- 1 arm would 1'10llll21lly rest by gravity against 1 the spring 5, extending down from the under side of the switch-arm 2, and would follow the switch-arm 2 when it is turned on its pivot. Spring 5 is held on the level of segment 6 when the arm is in the oii posit-ion by the studs 13, mounted on the base 1, and a stop 1 11 is provided to arrest the movement of the switch-arm when retracted by the spring 9. Mounted on the upper portion of the baseplate 1 is the self-reducing resistance 15, preferably consisting of one or more units constructed as described in my companion application above mentioned. Also mounted on the base-plate is an electromagnet 16,the polepieces of which extend in proximity to the path of movement of the curved cross-piece 11 and are preferably adjustable toward and away from that path to vary the air-gap. By reference to Fig. 2 it will be seen that the switch-arm is connected to a binding-post 17, which is to be connected to one side of the line, and that the segment 6 is connected to one terminal of the resistance 15, the other terminal of which is connected with the switchclip 12 and to a binding-post 18 for connection to the motor-armatine; also, that the magnet 16 is connected in shunt to the resistance 15.

As thus constructed the operation of the controller is as follows: One side of the line is connected to the bindingqiost 17, and the motor armature and iield are connected to the binding-posts 18 and 19, respectively. The motor-field and the retaining-magnet 8 in series therewith are thus constantly energized while the voltage is on the lines. To start the motor, the switch-arm 2 is turned on its pivot to the lowest position shown in dotted lines in Fig. 1, where it is held by the retaining-magnet 8 against the tension of spring 9. This movement brings the contact-spring 5 into ei'igagement with segment 6. thus closing circuit to the motor-armaturc through the self-reducing resistance and the coils of the magnet 16 in parallel. The current flowing in this circuit divides in passing through the two parallel paths in inverse relation to the resistance of these paths, and as the ohmic val no of the resistance 15 is high when circuit is iirst closed a comparatively large current flows through the magnet 16 and the latter is strongly energized. The auxiliary switclrarm 1O falls by gravity, with the arm 2, to the in termediate position shown in dotted lines in Fig. 1, where it is arrested by the magnet 16, the flux of which threads the iron cross-piece 11 on the switch-arm 10. The How of current through the self-reducing resistance 15 causes arm 10 and the latter falls by gravity to the lowest position shown in dotted lines in Fig. 1. where it engages the switch-clip 12, thus short-circuiting the resistance 15 and the magnet 16 and connecting the motor-armature directly across the lines. The ohmic value of the self-reducing resistance 15 is so proportioned that it admits current to the motor-armature in such amount as to bring the motor up to speed without dangerous overloading. and the proportions of magnetite or other ma terial and the silicate with which it is mixed may be varied to adjust the rate of decrease of the resistance as desired between wide limits. in every case, however, the decrease of the resistance is smooth and gradual as con tradistinguished from the step-by-step decrease obtained with the forms of motor-starting rheostats commonly used prior to my invention. The resistance of the coils of magnet 16 is so proportioned relatively to that of resistance 15 that the auxiliary switch-arm 16 is dropped after the ohmic value of resistance 15 has fallen to a predetermined amount. The time required for this drop in the resistance is practically constant under ordinary conditions of service' In case the voltage of the lines should fall abnormally the magnet 8 would be so weakened as to release the switcharm 2 and both arms would be retracted by the spring9 to the position shown in full lines in Fig. 1, in which position the circuit of the motor-armature is open.

In Figs. 4 and 5 1 have shown a modification of my invention designed for use with small motors, especially those which are l'irought up to speed before the load is thrown on. This controller is not automatic in its action, and for this reason is much more simple, and hence less expensive to construct, than that shown in Fig. 1. In this form of my invention 1 cmploy only one pivoted switch-arm, and 1 provide two contact-studs and L1 in the path of movement of this arln and connect these studs to opposite sides of the self-reducing resistance 15. Also I mount a strip of liber or similar material on the base-plate 1 to support the switch-arm when in the off position. To start the motor, the switch-arm is turned to bring it in contact with the stud 26. thus closing circuit through resistance 15 to the motor-armature. The arm is held in this po sition for a few seconds, during which the mo tor comes up to speed rapidly and the ohmic value of the resistance 15 falls gradually to the desired amount. Thearm is then moved into engaging relation to the stud 21, thereby short-circuiting the resistance 15. In this po sition the arm is held by the retaining-magnet 8, as before, and 111 case of a drop in the voltage it is released by the magnet and retracted to the oil position by the spring 9.

I have illustrated and described herein the form of my invention which I prefer to use; but I do not wish to be understood as limited in any way to this specific device, as many modifications can be made therein which I consider within the scope of my invention and which I aim to cover in the claims appended hereto.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. A motor-starting rheostat having a selfreducing resistance, means for closing circuit therethrough, a movable switch-arm, means whereby said arm when moved short-circuits the resistance, and means for retarding the movement of the switch-arm.

2. A motor-starting rheostat, having a selfreducing resistance, an electromagnet, means for closing circuit through the resistance and the coils of the electromagnet in parallel, a contact, a switch-arm movable into engaging relation to said contact to short-circuit the resistance, and means whereby the electromagnet retards the movement of the switch '-arm.

3. A motor-starting rheostat, having a selfreducing resistance, means for closing circuit thereth rough a contact, a switch-arm arranged to fall by gravity into engaging relation to said contact to short-circuit the resistance, and means for arresting the movement of the switch-arm until the ohmic value of the resistance falls to a predetermined amount.

4. A motor-starting rheostat, having a selfreducing resistance, means for closing circuit therethrough, a contact, a switch-arm movable i nto engaging relation to the contact to short-circuit said resistance, an armature carried by the switch-arm, and a magnet arranged to retard the movement of the switch-arm.

5. A motor-starting rheostat, having a selfreducing resistance, an electromagnet, means for closing circuit through the resistance and the coils of the electromagnet in parallel, a contact, a switch-arm movable into engaging relation to the contact to short-circuit the resistance, and an armature carried by the switch-arm, said electromagnet having its poles in proximity to the path of movement of said armature whereby movement of the switch-arm is retarded.

6. A motor-starting rheostat having a selfreducing resistance, means for closing circuit therethrough, a switch-arm movable to shortcircuit said resistance, an armature carried by the switch-arm, and a magnet by which the armature passes when the switch-arm moves to the short-circuiting position.

7. A motor-starting rheostat havinga selfreducing resistance, an electromagnet, means for closing circuit through the resistance and the coils of the electromagnet in parallel, a switch-arm movable to short-circuit the resistance, and an armature carried by theswitcharm, said electromagnet beingso arranged that said armature passes its poles when the switcharm moves to the short-circuiting position.

8. A motor-starting rheostat, having a resistance, two independently-movable switcharms, a contact cooperating with the first arm to close circuit through the resistance, a contact cooperating with the second arm to shortcircuit the resistance, means whereby movement of the first arm releases the second arm, and means for retarding the movement of the second arm.

9. A motor-starting rheostat, having a selfreducing resistance, two independently-movable switch-arms, a contact cooperating with the first arm to close circuit through the resistance, a contact cooperating with the second arm to short-circuit the resistance, means whereby movement of the first arm releases the second arm, and means dependent upon the ohmic value of the resistance for arresting the movement of the second arm.

10. A motor-starting rheostat, having a selfreducing resistance, two switch-arms independently pivoted at the same point, a contact cooperating with one arm to close circuit through the resistance, a contact cooperating with the other arm to short-circuit the resistance, means whereby movement of the first arm releases the second arm, means dependent upon the ohmic value of the resistance for retarding the movement of the second arm, means whereby both arms are held in the on position, and means for returning both arms to the ofi' position on failure of the line voltage. v

11. In a motor-starting switch, means for closingthe starting-circuit of the motor, a contact, a switch arm arranged to fall by gravity into engaging relation to said contact to establish the running connections of the motor, a magnet-winding adapted to retard said switch-arm, and means for impressing on the terminals of said magnet-winding an automatically-decreasing electromotive force.

12. In a motor-starting switclnmeans for closing the starting-circuit of the motor, a movable switch-arm adapted when moved to establish the. running connections of the motor, an armature carried by said switch-arm, an electromagnet having its poles in proX- imity to the path of movement of said armature whereby movement of the switch-arm is retarded, and means for impressing upon the terminals of said electromagnet an automatically-decreasing voltage.

In witness whereof I have hereunto set my hand this 12th day of May, 1904.

ERNEST SCHATTNER.

WVitnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

